A Vatican tribunal has thrown out some evidence gathered in the investigation of the Pope's butler, who is accused of stealing papers and passing them off to a journalist in the worst security breach in the Vatican's recent history.

The court also decided on Saturday during the first hearing of the case to separate the trial of the butler, Paolo Gabriele, and that of his co-defendant, Vatican computer expert Claudio Sciarpelletti.

Gabriele faces up to four years in prison if he is convicted of aggravated theft.

He has already confessed, saying he leaked the documents to shed light on what he called the "evil and corruption" in the church, and asked to be pardoned by the Pope.

Judge Giuseppe Dalla Torre set the next hearing for Tuesday, when Gabriele will be questioned.

Pope Benedict XVI's butler is accused of betraying him by leaking the secret documents stolen from his private Vatican apartments.

Gabriele, 46, was arrested earlier this year and spent two months in custody after the Pope turned detective and ordered a commission of cardinals to track down the source of the leak.

If convicted, the father-of-three Gabriele faces up to four years in prison.

Image Caption:TV journalists in front of the Vatican on the trial's opening day

The highly-sensitive documents alleged details of corruption within the Holy See, outlining how contracts were passed to favoured companies and individuals.

The documents also highlighted power struggles between ambitious cardinals vying for the Pope's favour.

Video:Pope Butler's Theft Trial Begins

Gabriele was held by Vatican gendarmes after a search of his apartment uncovered a host of personal letters written by the Pope and other officials.

They also found gifts that had been given to the Pontiff: a 100,000-euro cheque written out to Benedict from a South American university, a gold nugget and a 500-year-old book.

During his questioning, Gabriele allegedly insisted he "meant to give back" the items and also wrote to the Pope expressing his "sorrow".

He said he had not received "any money or other benefits", stressing he acted to "keep the Holy Father informed of certain facts and events".

Gabriele also told prosecutors he had acted because he had seen "evil and corruption everywhere in the Church" and wanted to stop it spreading.

He said: "I reached the point of no return. I was sure that a shock, perhaps by using the media, could be a healthy thing to bring the Church back on the right track."

The leaked documents were handed to Italian author Gianluigi Nuzzi in secret meetings in cafes close to the Vatican and used in his book His Holiness: Secret Papers Of Pope Benedict XVI.

He made sure to burn the originals and any copies that had been made, adding a flavour of Dan Brown to the whole scandal, inevitably dubbed "Vatileaks".

The IT expert Sciarpelletti has been charged with aiding and abetting the butler.

Only eight journalists were allowed into Saturday's hearing despite hundreds of accreditation requests. There was no live relay of the proceedings, with no TV crews or photographers permitted inside.

The tight security saw the eight journalists having to pass through a metal detector, handing over their pens in case they contained recording devices and swapping them for Vatican ones.

The tight access has raised questions about whether the Vatican is being totally transparent about the case.

There have been constant rumours in the Italian media since the scandal broke that Gabriele may have been a scapegoat and had the help of senior cardinals within the Church.

One theory is that the documents were leaked to undermine Cardinal Tarcisio Bertone, the Vatican's secretary of state.

Others speculated the leaking was aimed at Monsignor George Ganswein, the Pope's private secretary, who angered the Vatican old guard by giving interviews to Italian glossy magazines.

At some stage in the trial Monsignor Georg Ganswein will also testify. He had confronted the butler specifically over two papal letters, which only he had access to and which had appeared in Nuzzi's book.

The two-hour 15-minute hearing also heard how a video camera had been installed by police overlooking the entrance to Gabriele’s apartment to record comings and goings.